The present invention relates to a method to employ instrumentation to effectuate variation in lubricant flow rate or properties in response to actual engine conditions.
Diesel engines may generally be classified as slow-speed, medium-speed or high-speed engines, with the slow-speed variety being used for the largest, deep draft vessels and in industrial applications. Slow-speed diesel engines are typically direct coupled, direct reversing, two-stroke cycle engines operating in the range of about 57 to 250 rpm and usually run on residual fuels. These engines are of crosshead construction with a diaphragm and stuffing boxes separating the power cylinders from the crankcase to prevent combustion products from entering the crankcase and mixing with the crankcase oil. Medium-speed engines typically operate in the range of 250 to about 1100 rpm and may operate on the four-stroke or two-stroke cycle. These engines are trunk piston design, and many operate on residual fuel as well. They may also operate on distillate fuel containing little or no residua. On deep-sea vessels these engines may be used for propulsion, ancillary applications or both. Slow speed and medium speed marine diesel engines are also extensively used in power plant operations. The present invention is applicable to slow-speed diesel engines in both marine and power plant applications.
Each type of diesel engine employs lubricating oils to lubricate piston rings, cylinder liners, bearings for crank shafts and connecting rods, valve train mechanisms including cams and valve lifters, among other moving members. The lubricant prevents component wear, removes heat, neutralizes and disperses combustion products, prevents rust and corrosion, and prevents sludge formation or deposits.
In low-speed marine crosshead diesel engines, the cylinders and crankcase are lubricated separately, with cylinder lubrication being provided on a once-through basis by means of injection devices that apply cylinder oil to lubricators positioned around the cylinder liner. This is known as an xe2x80x9call-lossxe2x80x9d lubrication system. The cylinder oil is typically formulated to provide for good piston ring and cylinder liner wear control, as well as good oxidation and thermal stability, water demulsability, corrosion protection and good antifoam performance. Alkaline detergent additives are also present to neutralize acids formed during the combustion process. Dispersant, antioxidant, antifoam, antiwear and extreme pressure (EP) performance may also be provided by the use of suitable additives.
As engines produce higher power and are operated under more severe conditions, the lubricating oil""s required functionality and performance have dramatically increased. These increased performance demands have resulted in a corresponding increase in the lubricant""s expense. Lubricants are being made with increasingly sophisticated and expensive base stocks, including wholly synthetic base stocks. In addition, a wide variety of expensive additives, such as dispersants, detergents, antiwear agents, friction reducing agents, viscosity improvers, viscosity thickeners, metal passivators, acid sequestering agents and antioxidants are incorporated into the lubricants to meet functional demands.
Traditionally in Marine Diesel two stroke engines, the lubricant flow rate to the cylinder liner remained constant, or may have varied with respect to engine RPM. Early suggested improvements included setting this constant flow rate as a function of the sulfur content of the bulk bunker fuel taken as a one-time measurement before embarkation.
Studies have demonstrated that to achieve the bare minimum lubrication protection required for a two-stroke crosshead engine, lubricant flow should be modified in response to the prevailing engine operating and fuel conditions. See S. N. Yoo, O. S. Kwon, C. R. Son, xe2x80x9cService Experience of the Largest Diesel Engine Power Plant with Hyundaixe2x80x94MAN BandW 12K90MS-S Enginesxe2x80x9d, Proceedings of the 27th International Congress of Combustion Engines, p. 160, 2001. DE 10112691.3 incorporated this method by suggesting a near real-time variation of the feed rate of the lubricant to the cylinder liner in response to a real-time or near real time measurement of the sulfur content of the fuel entering the cylinder, or parameters which varied due to this sulfur content (eg. Wear, Fe content in the used lubricant, BN of the used lubricant).
The current inventors, in co-pending application U.S. Ser. No. 60/361376 Feb. 6, 2002 (herein incorporated by reference), improved upon all previous methods by demonstrating an apparatus and method for varying the properties of the lubricant itself in response to any engine condition of concern.
One major inefficiency of DE 10112691.3 is that it did not teach any possible means to obtain these measurements. Indeed, this should not have been unexpected; most devices used to measure used lubricant Fe content and BN did not produce results in near real-time or were too bulky to be included on an operating marine diesel two stroke engine. Similarly, the ""691 application neither provided nor suggested a method to actually measure the sulfur content of the fuel in a real-time or near real-time mode However, in developing their invention noted in the above co-pending application, the inventors also discovered a combination of instrumentation that would allow them to efficiently employ their invention. That instrument combination applies as well to an invention that only varied the feed rate of the lubricant to the cylinder liner. It is the object of the present invention to present a combination of instrumentation that will permit both their invention, and that suggested by DE 10112691.3, to effectively operate.
The present invention relates to a process of employing instrumentation for implementing the near real time varying of an xe2x80x9call lossxe2x80x9d diesel engine""s lubricating oil""s properties or flow rate in response to actual engine lubrication requirements. Preferably, the present invention provides a method for the in situ monitoring of the lubricating oil""s effectiveness in a diesel engine by measuring the Fe content of the used lubricant with miniaturized XRF technology, the actual fuel sulfur content using miniaturized XRF technology and the used lubricant""s BN with an IR measurement device, and for modifying the lubricant""s properties and/or flow rate in response to the actual wear or corrosion, or other needs of the machinery or engine. More preferably, the present invention is directed to the use of these instruments in a system that varies the feed rate or lubricant properties in a two-stroke crosshead diesel engine.